The original name was Labatt's Pilsener but it became known as simply Blue because of the colour of the label. (Thanks John) It's the name of the founder of this brewery... John Labatt
Labatt\'s Blue is called Blue because it was named for the Canadian Football team the Winnipeg Blue Bombers, not becasue of the label.
In Canada it is actually called Labatt\'s Blue and not Canadian Lager.